Renewable Energy Looks Swell

Sunday, March 22nd, 2015

Australia’s largest naval base now gets part of both its electricity and its fresh water courtesy of the Roaring Forties, westerlies, which blow between latitudes 40° S and 50° S:

Carnegie Wave Energy, in Perth, has been working since 1999 on what it calls CETO technology. Ceto was the ancient Greek goddess of sea monsters, and Carnegie’s particular monsters are buoys that resemble giant macaroons. They float a metre or two below the ocean’s surface, bobbing up and down in the swell and generating electricity as they do so. The current version, CETO 5, has a capacity of 240kW per buoy. Three of the beasts are now tethered to the sea bed 3km from HMAS Stirling, on Garden Island. They also help to run a desalination plant on the base, for fresh water is a valuable commodity in Western Australia’s arid climate.

CETO 5 Wave Energy Diagram

The buoys themselves are 11 metres across, made of steel and filled with a mixture of seawater and foam to give them a density slightly below that of water, so that they float. Being submarine means that, unlike previous attempts to extract power from waves, they are not subject to storms and the constant battering that life at the interface between sea and air brings. As Michael Ottaviano, Carnegie’s boss, observes, savvy swimmers in Australia know to dive under—not through—an approaching wave, to avoid getting smashed. The same applies to buoys.

Reverse-osmosis desalination plants tend to guzzle diesel or electricity, but the CETO 5 delivers water at a high enough pressure for reverse osmosis to happen automatically.

The next-generation CETO 6 buoys will measure 20 metres across and will generate a megawatt each, internally rather than at an onshore power plant, which means no pipe is needed; a submarine power cable will do instead. This could become economical:

Mr Ottaviano reckons that if CETO 5 were deployed en masse, in “wave farms” with a capacity of 25MW, it could produce electricity at a cost of 30-40 US cents a kW-hour, which is competitive with diesel. At a similarly large scale, CETO 6’s electricity would, Mr Ottaviano says, cost about 20 cents a kW-hour. Ultimately, he thinks, economies of scale could bring that down to 12-15 cents a kW-hour for a 100MW wave farm.


  1. Alrenous says:

    You can know a priori that wind power is worthless at industrial scale.

    Air’s density is only a bit more than a thousandth of water’s. That means the impulse at a given speed is a bit more than a thousandth.

    These, like hydroelectric generators, are reasonable but not spectacular. Scaling down multiple orders of magnitude is never going to be worthwhile.

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